JP2005064120A - Apparatus and method for plasma treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for plasma treatment with which an object to be treated is prevented from causing metal contamination, even if the object is affected by high-density plasma, surface waves, electric fields, etc. <P>SOLUTION: Gas supply pipes 5A and 5B, which are installed to the side wall of the chamber 1 of the plasma treatment device, are respectively disposed at positions sandwiching a gas-separating plate 2 which is provided in parallel with a dielectric window 9 separated from the window 9 in the chamber 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a plasma process in which an object to be processed is not contaminated with metal even under the influence of high-density plasma, a surface wave electric field, or the like.

  2. Description of the Related Art Plasma processing apparatuses are used to perform dry etching processing, ashing processing, and the like using microwave plasma on silicon wafers for manufacturing semiconductor devices, glass substrates for liquid crystal displays, and the like.

  There are several types of plasma processing apparatuses. For example, high-frequency power is supplied to an antenna that is an example of microwave introduction means, and microwave energy is applied to a process gas in a chamber (vacuum vessel) to generate plasma. There are those that are generated and subjected to a dry etching process or the like on an object to be processed using this plasma.

  More specifically, a dielectric window is provided in a ceiling portion of a chamber in which a stage for placing an object to be processed is provided. A waveguide having a slot antenna is provided above the dielectric window. In the waveguide, a plane (H plane) perpendicular to the microwave electric field direction faces the dielectric window, and a plane (E plane) parallel to the microwave electric field direction extends in a direction perpendicular to the H plane. In addition, a rectangular shape having a reflection surface that reflects the microwaves provided perpendicular to the H and E surfaces on the side opposite to the microwave introduction side, the microwaves are applied to the side in contact with the dielectric window. An opening (slot antenna) for introduction into the chamber through the dielectric window is provided (see, for example, Patent Document 1). A gas inlet for introducing a process gas into the chamber is provided near the dielectric window inside the chamber. (For example, see Patent Document 1).

With these structures, O ₂ , which is a process gas supplied into the chamber, is activated by plasma generated in the chamber, and ashing or the like is performed on the object by O radicals. In many cases, a fluorine atom such as CF ₄ is added to the process gas.
JP 2002-158210 A (paragraph number 0010)

In the conventional plasma processing apparatus as described above, as shown in the schematic diagram of FIG. 6, the workpiece W is disposed on the stage 32 provided at the center inside the chamber 31, and the plasma generation unit 33 is disposed on the stage. Directly above the workpiece W. In the case of such an apparatus configuration, since high-density plasma is generated in the vicinity of the dielectric window 35 into which microwaves are incident from the microwave waveguide 34, the density of plasma generated inside the chamber 31 is increased. Distribution becomes non-uniform. As a result, the cavity portion 36 that supports the dielectric window 35 is exposed to high-density plasma and is damaged. Further, the surface wave electric field is also damaged by F ions and F radicals. (Black circle in Fig. 6)
In particular, when using a process gas to which a fluorine atom such as CF ₄ is added, the damage is significant.

  When such damage is received, particles are generated thereby, causing metal contamination of the workpiece W.

  Usually, in the plasma processing apparatus, the inner wall (vacuum part) of the chamber 31 is coated with anodized or the like in order to prevent metal contamination. However, due to the influence of the high-density plasma and the surface wave electric field as described above, the alumite on the side wall of the cavity portion 36 or the chamber 31 may peel off and metal contamination may occur.

  The present invention has been made based on these circumstances, and provides a plasma apparatus and a method for preventing metal contamination of an object to be processed even under the influence of high-density plasma, a surface wave electric field, or the like. It is an object.

According to the present invention, the microwave introduction means for guiding the microwave traveling in the waveguide into the chamber and the dielectric window are provided, and the chamber is opposed to the dielectric window through a predetermined space. An electrostatic chuck for holding the object to be processed is disposed at the position, and a gas supply pipe for supplying gas into the chamber from the upper part of the chamber is provided, and the gas in the chamber is A plasma processing apparatus for processing the object to be processed by turning into plasma,
The plasma processing apparatus is characterized in that the gas supply pipes are respectively arranged at positions sandwiching a gas separation plate provided in parallel with the dielectric window in the chamber.

Further, according to the present invention, the gas supply pipe disposed above the gas separation plate supplies O ₂ gas not containing F into the chamber, while being disposed below the gas separation plate. The plasma processing apparatus is characterized in that a gas containing F is supplied into the chamber from a gas supply pipe.

Further, according to the present invention, the gas supply pipe disposed above the gas separation plate supplies O ₂ gas not containing F into the chamber, while being disposed below the gas separation plate. The plasma processing apparatus is characterized in that F atoms activated by thermally decomposing NF ₃ by heating are supplied into the chamber from the gas supply pipe.

According to the present invention, the microwave traveling in the waveguide is introduced into the chamber from the dielectric window via the microwave introduction means, and is sealed by the dielectric window and supplied into the chamber from the gas supply pipe. A plasma processing method for converting the processed gas into plasma and processing a workpiece held by an electrostatic chuck disposed in the chamber so as to face the dielectric window through a predetermined space,
The gas is supplied into the chamber by supplying an O ₂ gas containing no F from a gas supply pipe arranged above the gas separation plate arranged in the chamber and arranged below the gas separation plate. In the plasma processing method, a gas containing F is supplied from a gas supply pipe.

According to the present invention, the microwave traveling in the waveguide is introduced into the chamber from the dielectric window via the microwave introduction means, and is sealed by the dielectric window and supplied into the chamber from the gas supply pipe. A plasma processing method for converting the processed gas into plasma and processing a workpiece held by an electrostatic chuck disposed in the chamber so as to face the dielectric window through a predetermined space,
The gas is supplied into the chamber by supplying an O ₂ gas containing no F from a gas supply pipe arranged above the gas separation plate arranged in the chamber and arranged below the gas separation plate. The plasma processing method is characterized in that F atoms activated by thermal decomposition by heating NF ₃ are supplied from a gas supply pipe.

  According to the present invention, when a workpiece W is processed by a plasma processing apparatus, even if a gas containing F is used as a process gas, damage to the cavity portion can be eliminated, thereby extending the life of the apparatus. Is possible.

  Further, since no F atoms are present in the plasma region, damage to quartz and the side wall of the chamber is small. As a result, the reliability of the apparatus that can prevent metal contamination is improved.

  In addition, since fluorine can be used as the process gas, the resist stripping property of the workpiece W is improved, thereby improving the superiority of the process.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a downflow type microwave-excited plasma processing apparatus applied to ashing of a resist on an object to be processed (for example, a wafer).

  The interior of the chamber 1 is vertically divided into a plasma generation chamber 3 and a processing chamber 4 by a gas separation plate 2 made of a metal plate having gas passage holes arranged in a horizontal direction. The interior of the chamber 1 is surface treated with a fluororesin. In addition to the surface treatment with a fluororesin, alumite treatment or diamond coating may be applied.

  The gas separation plate 2 also serves as a shower plate so that gas flows evenly. For example, as shown in a plan view in FIG. 2 (a), a plurality of openings 2a are distributed over the entire surface, or radially as shown in FIG. 2 (b). The slits 2b are provided at equal angles.

  Two gas supply pipes 5A and 5B for supplying process gas to the inside of the chamber 1 are provided, and the gas supply pipes 5A and 5B are provided vertically through the side wall of the upper portion of the chamber 1 with the gas separation plate 2 interposed therebetween. Yes.

As the process gas, for example, when etching a thin film on the surface of the workpiece W, oxygen gas (O ₂ ) alone or fluorine gas such as CF ₄ , NF ₃ , SF ₆ is used as the oxygen gas. A mixed gas in which a gas is added or a gas in which hydrogen gas is added to these gases is used.

The process gas is supplied from the gas supply pipe 5 </ b> A provided above the gas separation plate 2 by supplying O ₂ gas not containing F into the chamber 1, while supplying the gas below the gas separation plate 2. From the tube 5B, a mixed gas containing fluorine gas such as CF ₄ , NF ₃ , SF ₆ or the like containing F, or a gas obtained by adding hydrogen gas to these gases is supplied into the chamber 1. I have to.

  In this case, since the exhaust port 6 sucked by a vacuum pump (not shown) is positioned below the stage 7 on which the workpiece W is placed, the gas flows downward from above in the chamber 1. It is flowing toward. Therefore, the gas containing F does not reach the plasma generation unit 2 above the gas separation plate 2.

  The stage 7 that holds the workpiece W includes an RF (radio wave) bias and a cooling mechanism (not shown), and is connected to an RF oscillator and a chiller, respectively. The exhaust port 6 is provided at the bottom of the chamber 1 in which the processing chamber 4 is formed, and one end of the exhaust pipe 8 is connected thereto. A vacuum pump (not shown) is connected to the other end of the exhaust pipe 8.

  A dielectric window 9 made of quartz glass, alumina, or the like is provided in an opening (cavity portion) 10 formed in the upper wall portion of the chamber 1, and the space between the opening 10 and the dielectric window 9 is not shown. The structure is sealed by an O-ring or the like.

  The rectangular waveguide 11 into which the microwave is introduced is disposed on the upper wall portion of the chamber 1 including the dielectric window 9. The waveguide 11 faces the dielectric window 9 as shown in FIGS. 3 and 4, and has a plane (H plane) perpendicular to the direction of the electric field of the microwave and a microwave extending in a direction perpendicular to the H plane. A surface parallel to the electric field direction (E surface) and a reflecting surface (short-circuit surface; R surface) for reflecting microwaves provided perpendicular to the H surface and the E surface on the side opposite to the microwave introduction side . Two slots (antenna means) 12a and 12b are opened along the E plane on the H plane in contact with the dielectric window 9.

  Next, a method of ashing the workpiece W (semiconductor wafer, liquid crystal glass substrate, etc.) having a resist pattern formed on the surface by a microwave-excited plasma processing apparatus having these structures will be described.

First, a glass substrate for liquid crystal, which is a workpiece W having a resist pattern formed on the surface thereof, is placed on the stage 7 inside the chamber 1. A vacuum pump (not shown) is operated to exhaust the gas inside the chamber 1 from the chamber 1 through the exhaust pipe 8. Next, as a process gas, for example, O ₂ gas is supplied into the chamber 1 through a gas supply pipe 5A provided above the gas separation plate 2, and a mixed gas of O ₂ and carbon tetrafluoride. Is supplied into the chamber 1 through a gas supply pipe 5B provided below the gas separation plate 2.

  When the inside of the chamber 1 reaches a predetermined pressure, plasma is generated in the plasma generation chamber 3 by introducing a microwave from a microwave generation source (not shown) into the waveguide 11. Ions are removed from the generated plasma by the gas separation plate 2, and active species are introduced into the processing chamber 4 through the openings 2 a (2 b) of the gas separation plate 2. Thereby, the active oxygen atoms in the plasma are reacted with the resist pattern on the surface of the workpiece W placed on the stage 7 to peel off the resist pattern.

In this case, since the mixed gas of O ₂ and carbon tetrafluoride is supplied into the chamber 1 from the gas supply pipe 5B provided below the gas separation plate 2, an opening for supporting the dielectric window 9 is provided. The cavity portion 12 in which 10 extends is not damaged by the F ions and F radicals by the surface wave electric field, and damage such as alumite can be prevented. As a result, the workpiece W can prevent metal contamination.

  Next, a modified example of the above-described plasma processing apparatus will be described.

NF ₃ gas may be used as a dry etching gas or a cleaning gas that is a process gas in a plasma processing apparatus. That is, when a Si wafer is etched with NF ₃ gas ionized in a discharge in an NF ₃ gas atmosphere, the reaction product becomes a volatile substance. Therefore, carbon (C) or sulfur is compared with etching in a conventional fluorocarbon plasma. There is an advantage that there is no reaction residue contamination on the wafer surface due to (S). Furthermore, since there is no reaction residue contamination, there is an advantage that the etching rate is increased. From such a point of view, NF ₃ gas is frequently used. NF ₃ gas is very stable at room temperature, but can be thermally decomposed by heat treatment and converted to F ₂ , HF, or the like.

  FIG. 5 is a schematic diagram showing an outline of the plasma processing apparatus of this modification. The same functional parts as those in FIG. 1 are denoted by the same reference numerals and their description is omitted. The basic structure of the plasma processing apparatus is the same as that of the plasma processing apparatus shown in FIG. 1, but in the case of this modification, two gas separation plates 2 and 13 are provided.

  That is, two gas supply pipes 5A and 5B for supplying a process gas to the inside of the chamber 1 are provided, and are arranged vertically through the gas separation plate 2 so as to penetrate the upper side wall of the chamber 1. Yes. A second gas separation plate 13 is provided in parallel with the gas separation plate 2 below the gas supply pipe 5 </ b> B provided under the gas separation plate 2. An MFC (mass flow controller) 14 and a heater 15 are connected to the gas supply pipe 5B provided under the gas separation plate 2.

The process gas is supplied from the gas supply pipe 5 </ b> A provided above the gas separation plate 2 by supplying O ₂ gas not containing F into the chamber 1, while the gas supply pipe below the gas separation plate 2. From 5B, NF ₃ is heated to 300 ° C. to 800 ° C. by the heater 15 to be thermally decomposed, and activated F atoms are generated and supplied into the chamber 1. That is, instead of F radicals, active F atoms generated by using thermal decomposition of NF ₃ are supplied to the surface of the workpiece W from a position isolated from the plasma region. Further, since the exhaust port 6 sucked by a vacuum pump (not shown) is located below the stage 7 holding the workpiece W, the inside of the chamber 1 is directed from above to below. It is flowing. Therefore, the gas containing F does not reach the plasma generation unit 3 above the gas separation plate 2. That is, the gas separation plate 2 plays a role of gas separation.

  Further, the two gas separation plates 2 and 13 can cut the ions from the plasma and reduce the influence of the plasma heat distribution. Moreover, since the gas flow can be controlled, the uniformity of the etching process of the workpiece W can be improved.

  Even in this case, the cavity portion 12 extending from the opening 10 that supports the dielectric window 9 is not damaged by the F ions and F radicals by the surface wave electric field, thereby preventing damage such as alumite. Can do. As a result, the workpiece W can prevent metal contamination.

The schematic diagram which shows the plasma processing apparatus of a down flow type microwave excitation. (A) is a top view of a gas separation plate, (b) is a top view of another gas separation plate. Explanatory drawing of a waveguide. The perspective view of a waveguide. The schematic diagram which shows the outline | summary of the modification of a plasma processing apparatus. The schematic diagram of the principal part of the conventional plasma processing apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Chamber 2, 13 ... Gas separation plate, 3 ... Plasma production chamber, 4 ... Processing chamber, 5A, 5B ... Gas supply pipe, 7 ... Stage, 9 ... Dielectric window, 11 ... Waveguide, 12 ... Cavity portion

Claims (5)

Microwave introduction means for guiding the microwave traveling in the waveguide into the chamber and a dielectric window, and an object to be processed at a position facing the dielectric window with a predetermined space in the chamber An electrostatic chuck for holding the gas is disposed, and a gas supply pipe for supplying gas into the chamber from the upper part of the chamber is provided, and the gas in the chamber is converted into plasma by the microwave. A plasma processing apparatus for processing an object to be processed,
The plasma processing apparatus, wherein each of the gas supply pipes is disposed at a position sandwiching a gas separation plate provided in parallel with the dielectric window in the chamber. From the gas supply pipe disposed above the gas separation plate, O ₂ gas not containing F is supplied into the chamber, while from the gas supply pipe disposed below the gas separation plate. 2. The plasma processing apparatus according to claim 1, wherein a gas containing F is supplied into the chamber. From the gas supply pipe disposed above the gas separation plate, O ₂ gas not containing F is supplied into the chamber, and from the gas supply pipe disposed below the gas separation plate. 2. The plasma processing apparatus according to claim 1, wherein F atoms activated by thermal decomposition by heating NF ₃ are supplied into the chamber. The microwave traveling in the waveguide is introduced into the chamber from the dielectric window through the microwave introduction means, and the gas supplied into the chamber from the gas supply pipe sealed by the dielectric window is turned into plasma, A plasma processing method for processing an object to be processed held by an electrostatic chuck disposed in the chamber so as to face the dielectric window through a predetermined space,
The gas is supplied into the chamber by supplying an O ₂ gas containing no F from a gas supply pipe arranged above the gas separation plate arranged in the chamber and arranged below the gas separation plate. A plasma processing method, wherein a gas containing F is supplied from a gas supply pipe. The microwave traveling in the waveguide is introduced into the chamber from the dielectric window through the microwave introduction means, and the gas supplied into the chamber from the gas supply pipe sealed by the dielectric window is turned into plasma, A plasma processing method for processing an object to be processed held by an electrostatic chuck disposed in the chamber so as to face the dielectric window through a predetermined space,
The gas is supplied into the chamber by supplying an O ₂ gas containing no F from a gas supply pipe arranged above the gas separation plate arranged in the chamber and arranged below the gas separation plate. A plasma processing method characterized in that NF ₃ is heated and thermally decomposed to supply activated F atoms from a gas supply pipe.

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